Compressor for hydraulic brakes



June 27,1939. R, A. GOEPFRICH 2,163,874

COMPRESSOR FOR HYDRAULIC BRAKES Filed Oct. ,23, 1936 2 She'ets-Sheet l `)une 27, 17939.

R. A. GOEPFRICH COMPRESSOR FOR HYDRAULIC BRAKES 2 Sheets-Sheet 2 Filed oct. 25, 195s INVENTOR PH 67. Chipre/cw ATTORNEY.

Egg-az,

Patented June x27, 1939 UNITED STATI-:s

PATENT OFFICE Application october 23, 1936, serial'No. 107,239

11 Claims.

This invention relates to fluid pressure braking systems, and more particularly to fluid pressure producing devices for such systems.

In conventional fluid pressure braking systems l having a, fluid pressure producing device includving Va uid reservoir, a cylinder supplied therefrom, and a piston movable in the cylinder for producing pressure, the cylinder generally has two ports providing communications between the cylinder and the reservoir. These ports are known in the artY as the supply port and the compensating port. The latter is located slightly in advance of a flexible Icup seated on the head of the piston when theA piston is in fully retracted position. When the piston moves on its compression stroke, the ypressure created in the cylinder forward of the piston forces the Wallof the cup into the compensating port and this results in serious injury to the cup, resulting in rendering the device inoperative. It is the aim of the present invention to overcome this undesirable condition.

Anl object of the invention is to provide a fluid pressure producing device including a fluid reservoir, a cylinder supplied therefrom, and a piston movable in the reservoir for produc/ing pressure, and to eliminate from the structure such communications between the cylinder and the reservoir as may prove injurious to the piston.

Another object of the invention is to provide a fluid pressure producing device having a piston provided with means for by-passing uid when the piston is in retracted position.

Another object of the invention is to provide y, ling the communication between the reservoir and that 'portion of the cylinder forwardrof .the piston.

A feature of the invention is to provide a piston having a passage therethrough, and a valve of a particular structure for control of the passage.

Another feature of the invention is to provide a fluid pressure producing device -including a reservoir, a cylinder associated therewith, apiston movable in the cylinder, a supply tube extending from the reservoir into the'cylinder, and a valve in the head of thepiston adapted to be tripped by the tube.

Other objects and advantages of the invention will appear from the following description taken in connection with the drawings forming a part of this specication, and in which,

Fig. 1 is a diagrammatical illustration of a fluid brake system embodying the invention;`

Fig; 2 is a vertical, sectional view of the fluid pressure producing device illustrating-the piston thereof in retracted position;

(Cl. Gil-54.6)

Fig. 3 is a fragmentary view of the fluid pressure producing device illustrating the piston thereof on its compression stroke;

Fig. .4 is an enlarged detail view of the valve in the head of the piston of the iluid pressure producing device;-

Fig. 5 is a vertical, sectional view of a modication of the-fluid pressure producing device illustrating the piston thereof in its retracted position; and Y Fig. 6 Vis `a modification of the valve in the head of the piston of the fluid pressure producing device.

Referring to the drawings for more specific details of the invention, I0 represents a fluid reservoir having a filling opening l2 which may be closed as by a plug- I4 having a plurality of openings IB for venting the reservoir to the at- ,mosphere 4 A cylinder I8 formed integral with the reservoir at the base thereof has an opening in its wall in which is mounted a hollow plug 20 providing a communication between the cylinder and the reservoir, and a head 22 lltted on the cylinder has /an opening providing a discharge port 24 for the cylinder.

A fluid pressure delivery pipe 26 suitably con-y nected to the discharge port 24 of the cylinder has branches connected respectively to fluid pressure actuated motors 28 arranged in pairs, one

pair for the actuation of the brakes associated' with the front Wheels of a vehicle, and another for actuation of the brakes associated with the rear Wheels of the vehicle.

The brakes may be of conventional type each including a fixed support or backing plate 30, a rotatable drum 32 associated with the backing plate, a pair of correspondinginterchangeable friction elements or shoes 34 and 36 pivoted on the backing plate, and a motor corresponding to the motor 28 mounted on the backing plate between the shoes and operative to actuate the shoes into engagement with the braking surface of the drum 28 against the resistance of a retractile spring 38 connecting the-shoes.

A piston 4|] reciprocable in the cylinder I8 is retained against displacement by a washer 42 held against an annular shoulder in the open end of the cylinder by a retaining ring 44 seated in a circumferential groove in the wall of the cylinin which is seated a leak-proof washer 54 for inhibiting the seepage of lluid from the cylinder past the piston.

The head of the piston also has a circumferential groove adjacent its face in which is seated a leak-proof Washer 56 for inhibiting the seepage of fluid past the piston, and the face of the piston is slightly reduced in cross-section so that upon a compression stroke of the piston the pressure on the fluid in the cylinder forward of the piston may readily act upon the washer to spread the lips thereof so as to provide a more efficient seal between the piston and the wall of the cylinder.

The head of the piston has a coaxial passage 58 opening into a concentric frustro-conical recess 60 in the face of the piston, the latter providing a valve seat of considerable magnitude, the purpose of which will hereinafter appear. The passage 58 and the recess 60 provide a communication between the chamber 52 and that portion of the cylinder I8 forward of the piston. This communication is controlled by a valve 62 having a stern 64 slidable in the passage 58. The stem is suitably channeled as at 66 to provide for the free flow of fluid through the passage 5B and is longitudinally slotted for the reception of a retaining pin 08. The stem may also be axially bored for the reception of a light spring 'l0 interposed between the free end of the stem and the retaining pin 68 for urging the valve to its seat. The head of the valve has an extension l2 terminating in a knob 14, and a leak-proof washer 16 sleeved on the extension and retained against' displacement by the knob has a rim conforming to the wall of the frustro-conical recess so as to effectively seal the valve when it is in closed position.

It is to be especially noted that the valve 62 is formed with a conical metallic head 63 which is arranged to contact the frustro-conical recess 60 and forma primary seal. The washer 16 aids in sealing but the pressure of the liquid is taken by the metallic head 63 and thus the rubber element A recess 18 in the back of the piston receives a ball 80 formed on one end of a rod 82 having thereon an adjustable collar 84. The ball is suitably secured in the socket as indicated at 86 so that the rod and pistcn may move in unison. A

coil spring 88 is sleeved on the rod between the collar 84. and the washer 42 in the open end of the cylinder. This spring serves to return the rod and hence the piston connected to the rod to their retracted positions, and a flexible boot sleeved on the rod and connected between the collar 04 and the open end of the cylinder excludes dust and other foreign substances from the cylinder. As shown, the rod 82 is connected to a foot pedal lever 92 pivoted on a flxed support 94, and the foot pedal lever may be connected by a retractile spring 96 to a fixed support.

Modifications of the invention are illustrated in Figs. 5 and 6. In the modification of Fig. 5 a reservoir |00 has an opening |02 in its top, and formed on the perimeter defining the opening is a flange |04 having a circumferential groove |08, the purpose of which will hereinafter appear. The reservoir is provided with a filling opening |08 which may be closed as by a plug ||0 and.

depending from the reservoir in axial alignment with the opening |02 and in direct communication with the reservoir is a cylinder I2 having a head ||4 provided with a discharge port ||6 which `rmay be suitably connected to a fluid pressure delivery pipe ||8 corresponding to the fluid pressure delivery pipe illustrated in the preferred form of the invention.

A piston |20 reciprocable in the cylinder seats when 1n its retracted position on a washer |22- held against an annular shoulder in the open end of the cylinder by a retaining ring |24 seated in a groove in the wall of the cylinder. The piston has a reduced body portion |28 (providing in conjunction with the wall of the cylinder an annular chamber |30 communicating with the reservoir by Way of a plurality of spaced ports |32), which is slotted as indicated at |34 for the reception of a pin or stop |36 mounted in the wall of the cylinder. The head of the piston |2| is formed with a groove |31 in which it carries a leak-proof washer |30. It is provided with an axial passage |40 controlled by a valve |42 urged to its seat by a spring |44 interposed between the valve and the head of the cylinder and retained in open position when the piston is in its retracted position by the stop |36.

A rod |45 has one of its ends suitably connected to the piston |20 and its other end adjustably connected to a clevis |48 having thereon a collar |50 connected as by a flexible boot |52 to the flange |04 on the reservoir for the exclusion of dust and other foreign substances from the reservoir, and pivotally connected to the clevis |48 is a conventional foot pedal lever |54 which may be connected by a retractile spring, not shown, to a fixed support, also not shown. The rod |46 extends through the opening |02 and the passage of the rod through they opening is sealed by a portion |021; of the boot |52.

In the form shown in Fig. 6 the head |2| is shortened, the groove omitted and the cup |38 positioned adjacent to the lower end. An additional bearing surface |3| is provided adjacent to the upper end of the piston and ports |32 provide means by which the reservoir |00 may communicate with the chamber |30. The valve |42 is provided with a metallic head |43 which is arranged to seat on a washer 11 secured to the piston head |2|.

In a normal operation of either the preferred or the modified form of the invention, assuming that the system is filled with a suitable fluid, upon depressing the foot pedal lever force is transmitted from the lever through the rod to the piston to move the piston on its compression stroke. As the piston moves on its compression stroke, the valve in the head of the piston is released, and is urged by the spring 10 or |44, as the case may be, to its seat. Thereafter the pressure on the fluid in the cylinder forwardbf the piston is received on the head of the piston and the fluid is displaced from the cylinder through the fluid pressure delivery pipe 24 and its respective branches to the fluid pressure actuated motors 28 resulting in actuation of the motors with the consequent spreading of the shoes 34 and 36 into drum engagement to effectively retard rotation of the drum.

Upon the completion of a braking operation, the operator releases the foot pedal lever, whereupon the retractile spring connected to the lever becomes effective to return the lever to its retracted position. As the lever returns to its retracted position, the piston also moves to its retracted position under the influence of the spring 0B, or the spring |44, as the case may be. As the piston moves to its retracted position, a partial vacuum is created in the cylinder forward of the piston, resulting in cracking the valve 60 or |42, as the case may be, and drawing fluid from the reservoir into the cylinder to completely fill the cylinder, and when the piston is returned to its fully retracted position the hollow plug 20 or the stop |36 engages the valve 60 or |42 and retains the valve open so as to establish communication between the reservoir and that portion of the cylinder forward of the piston. 4

During the retraction stroke of the" piston ,fluid is returning from the fluid pressure actuated motors 28 and the pipe system connecting these motors to the cylinder under the influence of the retractile springs 38 connected between the `r friction elements. The fluid returned from the fluid pressure actuated motors 2B and the piping system connecting these motors to the cylinder I8 may be in excess of the quantity of fluid required to ll the cylinder, and this excess iluid is returned by way of the valve in the` head of the piston, the chamber back of the head of the piston, and the hollow plug to the reservoir.

Although thisinvention has been described in. connection with certain specific embodiments,y

the principles involved are susceptible of numerous other applications that will readily occur to persons skilled in the art. The invention is,

therefore, to be limited only by the scope of the holding the valve open when the piston is in fully retracted position.

2. A fluid pressure producing device comprising a reservoir, a cylinder supplied therefrom, a piston movable in the cylinderhaving a passage therethrough, a valve for controlling the passage, means for urging the valve to its seat, and means comprising a hollow tube forming a liquid passageway from said reservoir to said cylinder for holding the valve open when the piston is in fully retracted position.

3. A fluid pressure producing devicev comprising a reservoir, a cylinder supplied therefrom, a piston reciprocable in the vcylinder havingy a passage therethrough, a spring-pressed valve controlling the passage, sealing means carried by the valve, and means comprising a hollow tube forming a liquid passageway from said reservoir to said cylinder for holding the valve open when the piston is in fully retracted position.

4. A fluid pressure producing device comprising a reservoir, a cylinderl associated therewith, a piston movable in the cylinder having a passage therethrough, a valve controlling the passage, and a supply tube extending from the reservoir into the cylinder arranged to trip the ,valve when the piston is returned to its retracted position.

5. A fluid pressure producing device comprising a reservoir, a' cylinder rassociated therewith,

7o tube extending from the reservoir into the cylina`y piston reciprocable in the cylinder having a.

passage therethrough, a valve for controlling the passage, a sealing member carried by the valve, means urging the valve to its seat, and a supply der arranged to retain the valve in open position when the piston is in fully retracted position.

6. A fluid pressure producing device'comprising al reservoir, a cylinder associatedtherewith,

a piston reciprocable in the cylinder having an axial passage and a frustro-conical recess in its face communicating with the passage, a valve for controlling the passage having a stem slidable therein and a head adapted to seat in .the recess, a flexible member on the head of the valve cooperating with the wall of the recess to seal the valve, means for urging the valve to its seat, and a supply tube extending from the reservoir into the cylinder y,and arranged to retain the valve open when the piston is in fully retracted position.

7; A fluid pressure braking system comprising a reservoir, a cylinder associated therewith, a piston reciprocable in the cylinder having a passage therethrough, a valve controlling the passage, means for urging the valve to its seat, a supply tube extending from the reservoir into the cylinder and arranged to retain the valve open when the piston is in fully retracted position, fluid pressure actuated motors operatively connected to the cylinders, elements actuated by the motors, and means for actuating the piston.

8. A fluid pressure braking system comprising a reservoir, a cylinder associated therewith, 'a

pist-on reciprocable in the cylinder having an axial passage and a frustro-conical recess in its face providing a passage through the piston, a valve controlling the passage having a part slidable in the axial port kand another part adapted to seat in the recess, a flexible sealing member carried by the valve, means urging the valve to its seat, a supply tube extending from the reservoir into the cylinder and arranged to retain the valve open when the piston is in fully retracted position, fluid pressure actuated motors operatively connected to the cylinder, elements actuated by the motors, and means for actuating the piston. I

9. A fluid pressure producing device comprising a reservoir; a cylinder associated therewith; a piston movable in the cylinder'having an axial passage therethrough and being formed with a recess communicating with the passage; a valve controlling the passage comprising a guide portion slidable in said passage, a head portion seating in the recess, and a sealing memcomprising a stem slidable ,in said passage, a

sealing head seating in the recess, and a sealing member carried by the head; and a supply tube extending from the reservoir into the cylinder arranged to trip the valve when the piston is returned to its retracted position.

f 11. A fluid pressure producing device comprising a reservoir; a cylinder associated therewith; a2 piston having a frusto conical valve seat movablein the cylinder, and haying a passage therethrough; a valve comprising a metallic frusto corneal ,portion and a, rubber washer secured thereto controlling the passage, and a` supply tube extending from the reservoir into the cylinder arranged to trip the valve when the' pistonis returned to its retractedposition.

RUDOLPH A. GOEPFRICH. 

